Power management is an important field in modern electronics. It is usually desirable to ensure low power consumption for electronic devices in general and integrated circuits (ICs) in particular because low power usage promotes increased efficiency and reduces heat dissipation.
For most existing silicon based circuits, it is usually the case that given a specific circuit, increasing the operating voltage of the circuit will result in increased power consumption.
An important characteristic of circuits or portions of circuits is their speed. The speed of a circuit is related to the time it takes for the circuit to produce a stable and correct output signal after being provided with stable input signals. Speed is a significant characteristic, because faster circuits allow for higher clock frequencies (or alternatively, for more processing to be performed without intermediate latching), and thus generally improve the performance of larger integrated circuits. Speed may depend on the operating voltage of the circuit. Usually, higher voltages result in higher speeds. It should be noted that as used herein, the term speed differs from the term clock speed.
Therefore, while it may be desirable to decrease the operating voltage of a circuit in order to decrease the power it uses, this may be detrimental as it may slow the circuit down. If the circuit is slowed down to the point where stable signals cannot be produced in time to be latched, then the entire circuit may fail as the result of reduced voltage (or alternatively, the circuit's clock speed may need to be decreased). Thus, for many existing circuits, voltages are kept well within predefined safe tolerances in order to ensure that the circuit is fast enough for normal operation under various environmental conditions. This often results in relatively high voltage, which in turn results in relatively high power requirements.
Some existing circuits use high level information about the operations a circuit is about to perform in order to control the voltage of the circuit. For example, it may be known that a CPU may be able to perform certain simple operations (or a low number of operations) at a lower speed (and thus at a lower voltage). Thus, the CPU may determine whether the upcoming operations it is about to perform may allow it to operate at a lower speed and decrease its voltage accordingly. Chips produced by Transmeta Corporation of Santa Clara, USA may utilize similar technology.